A phthalocyanine compound is useful as a coating, printing ink, catalyst or electronic material. In particular, the application of such a phthalocyanine compound to an electrophotographic photoreceptor, an optical recording material, and a photo-electric converter has been extensively studied.
An electrophotographic photoreceptor has recently been increasingly demanded for the expansion of the sensitive wavelength range from the sensitive range of the prior art organic photoconductive material to the wavelength range of near infrared semiconductor laser (780 to 830 nm), for the use as a photoreceptor for digital recording in laser printer. In this respect, squarium compounds (as disclosed in JP-A-49-105536 and JP-A-58-21416 (The term "JP-A" as used herein means an "unexamined published Japanese patent application), triphenylamine trisazo compounds (as disclosed in JP-A-61-151659), phthalocyanine compounds (as disclosed in JP-A-48-34189 and JP-A-57-148745), etc. have been proposed as photoconductive materials for semiconductor laser.
Organic photoconductive materials to be used as photoreceptors for semiconductor laser must be sensitive up to long wavelength range. The photoreceptors formed by the organic photoconductive materials must exhibit a high sensitivity and an excellent durability. The foregoing prior art organic photoconductive materials cannot sufficiently meet these requirements.
In order to overcome these difficulties, the relationship between the crystal form and the electrophotographic properties has been studied on the organic photoconductive materials. In particular, many reports have been made on phthalocyanine compounds.
In general, phthalocyanine compounds are known to exhibit various crystal forms depending on preparation method and processing methods. It is also known that the difference in the crystal form has a great effect on the photoelectric properties of the phthalocyanine compounds. As the crystal forms of phthalocyanine compounds such as copper phthalocyanine, the stable .beta.- form as well as .alpha.-, .pi.-, .chi.-, .rho.-, .gamma.-, and .delta.-forms are known (as disclosed in U.S. Pat. Nos. 2,770,629, 3,160,635, 3,708,292, and 3,357,989). JP-A-50-38543 describes the relationship between the difference in the crystal form and the electrophotographic sensitivity of copper phthalocyanine.
With reference to gallium phthalocyanine prepared by an acid pasting process, JP-A-1-221459 describes two crystal forms and their electrophotographic properties, and Bull. Soc. Chim. France, vol. 23 (1962) describes preparation of a hydroxygallium phthalocyanine by acid-pasting chlorogallium phthalocyanine with sulfuric acid.
However, the phthalocyanine compounds which have been heretofore proposed, if used as photosensitive materials, are not sufficient in respect to photosensitivity and durability. It has thus been desired to develop a phthalocyanine compound having a new crystal form suitable as a photosensitive material which exhibits an improved photosensitivity and durability while making the best use of the feature of phthalocyanine compounds.
The present invention has been worked out on the basis of the foregoing circumstances.